Electronically controlled range valve for multi-speed planetary transmission

ABSTRACT

A shift by wire control for a multi-speed vehicle transmission is provided. The control includes a shift by wire shift valve in fluid communication with other shift valves and clutch trim valves to provide double blocking features in the neutral range and a reverse range. The shift by wire valve is configured with multiple differential areas to provide failure modes for all forward ranges.

TECHNICAL FIELD

The present invention relates generally to power transmissions for motorvehicles, and more particularly, to a shift by wire control system for apower transmission including an electronically controlled range valve.

BACKGROUND

An electro-hydraulic control system controls shifting and operation ofautomatic vehicle transmissions. To permit shifting by the vehicleoperator, the electro-hydraulic control system typically includes eithera manual valve or a shift by wire valve.

In a manual valve electro-hydraulic control system, the vehicle operatormanually changes the position of the valve to accomplish certain shifts,for example, to initiate movement of the vehicle from a non-moving stateto a moving state or vice versa, or to change the direction in which thevehicle is moving (i.e., shifts from neutral to a forward range, fromneutral to a reverse range, from a reverse range to a forward range,from a reverse range to neutral, from a forward range to neutral, orfrom a forward range to a reverse range).

In a shift by wire control system, at least some of the inputs that areused to initiate shifting are in the form of electrical signals ratherthan hydraulic or mechanical forces. Instead of a manual shift selector,a push button range selector may be used in a shift by wire system.Activation of a push button or similar actuator by the vehicle operatorsends an electrical signal to an electronic control unit. The electroniccontrol unit executes computer logic to determine which valve(s) in theelectro-hydraulic control system need to change position in order forpressurized hydraulic fluid to be directed to the appropriate clutchesto accomplish the requested shift. The electronic control unit sendselectrical signals to solenoid valves of the electro-hydraulic controlsystem, which initiate the valve position changes required to accomplishthe requested shift.

SUMMARY

According to one aspect of the present invention, an electro-hydrauliccontrol for a multi-speed vehicle transmission is provided. Theelectro-hydraulic control includes an electrical control configured toreceive shift request signals from an electronic range selector of thetransmission, first, second, and third electro-hydraulic actuators eachconfigured to receive electrical signals from the electrical control,first, second and third shift valves each being in fluid communicationwith the first, second, and third electro-hydraulic actuators to receivepressurized hydraulic fluid output by the electro-hydraulic actuatorsand being in fluid communication with each other to selectively deliverpressurized hydraulic fluid to at least one shift mechanism of thetransmission, a fourth electro-hydraulic actuator configured to receiveelectrical signals from the electrical control, a fourth shift valveconfigured to selectively deliver pressurized hydraulic fluid to atleast one shift mechanism of the transmission, the fourth shift valvebeing controllable by the fourth electro-hydraulic actuator to achieve afirst position when the fourth electro-hydraulic actuator is notelectrically actuated and a second position when the fourthelectro-hydraulic actuator is electrically actuated, and a plurality offluid passages selectively coupling the first, second, third, and fourthshift valves such that a neutral or reverse range can be achieved by thetransmission when the fourth shift valve is in either the first positionor the second position, and a forward range can be achieved by thetransmission only when the fourth shift valve is in the second position.

The fourth shift valve may have a first fluid chamber fluidly coupled toa first shift mechanism and a second fluid chamber fluidly coupled to asecond shift mechanism, where the first shift valve has a third fluidchamber fluidly coupled to a third shift mechanism, the third shiftvalve has a fourth fluid chamber fluidly coupled to a fourth shiftmechanism, and the first shift valve has a fifth fluid chamber fluidlycoupled to a fifth shift mechanism of the transmission. The second shiftvalve may be fluidly coupled to the third shift mechanism through thefirst and third shift valves in a first reverse range and the secondshift valve may be fluidly coupled to the fifth shift mechanism throughthe first, third, and fourth shift valves in a second reverse range.

The electro-hydraulic control may include a torque converter clutchcontrol valve, wherein the torque converter clutch control valve iscoupled to at least one of the first, second, third and fourth shiftvalves.

The plurality of fluid passages may selectively couple the first,second, third, and fourth shift valves such that a first reverse rangecan be achieved whether the fourth shift valve is in the first positionor the second position. The plurality of fluid passages may selectivelycouple the first, second, third, and fourth shift valves such that aneutral range can be achieved whether the fourth shift valve is in thefirst position or the second position. The plurality of fluid passagesmay selectively couple the first, second, third and fourth shift valvessuch that at least two of the shift valves are required to changeposition in order for the transmission to shift from a neutral range toa forward range.

The electro-hydraulic control may include first and second trim systemseach configured to receive electrical signals from the electricalcontrol and control the rate at which fluid pressure is delivered to theshift mechanisms of the transmission via the first, second, third, andfourth shift valves, wherein the first trim system is directly fluidlycoupled to the first shift valve, the second trim system is directlyfluidly coupled to the second shift valve, the second trim system isfluidly coupled to the third shift valve via the second shift valve, andthe second trim system is fluidly coupled to the first shift valve viathe second and third shift valves.

The fluid passages may selectively couple the first, second, third andfourth shift valves such that at least one of the trim systems and atleast one of the shift valves are required to be actuated in order forthe transmission to shift from a neutral range to a reverse range.

According to another aspect, an electro-hydraulic control for amulti-speed vehicle transmission is provided, including an electricalcontrol configured to receive shift request signals from an electronicrange selector of the transmission, at least one trim system actuatableby the electrical control to control the rate of delivery of pressurizedhydraulic fluid to at least one shift mechanism of the transmission,first, second, and third electro-hydraulic actuators each configured toreceive electrical signals from the electrical control, first, secondand third shift valves each being in fluid communication with the first,second, and third electro-hydraulic actuators to receive pressurizedhydraulic fluid output by the electro-hydraulic actuators and being influid communication with each other to selectively deliver pressurizedhydraulic fluid to at least one shift mechanism of the transmission, afourth electro-hydraulic actuator configured to receive electricalsignals from the electrical control, and a fourth shift valve configuredto selectively deliver pressurized hydraulic fluid to first and secondshift mechanisms of the transmission, the fourth shift valve beingcontrollable by the fourth electro-hydraulic actuator to achieve a firstposition when the fourth electro-hydraulic actuator is not electricallyactuated and a second position when the fourth electro-hydraulicactuator is electrically actuated, the fourth shift valve beingconfigured to maintain the first position if the fourth shift valve isin the first position when an electrical failure occurs, and the fourthshift valve being configured to maintain the second position if thefourth shift valve is in the second position and a trim system isactuated when an electrical failure occurs.

The fourth shift valve may have at least first, second and thirdspaced-apart lands, where the first and second lands define a secondfluid chamber that is in fluid communication with the second shiftmechanism and the second and third lands define a first fluid chamberthat is in fluid communication with the first shift mechanism. Fluid inthe first and second fluid chambers of the fourth shift valve may be atan exhaust pressure in neutral and reverse ranges during normaloperation and also during an electrical failure.

The first land may have a first diameter, the second land may have asecond diameter, the third land may have a third diameter, where thesecond diameter is larger than the first diameter, and the thirddiameter is larger than the second diameter. The electro-hydrauliccontrol may apply fluid pressure to a differential area of the thirdland of the fourth shift valve to keep the fourth shift valve in thesecond position during an electrical failure occurring in a low forwardrange. The low forward range may be a forward range lower than a fourthforward range. The electro-hydraulic control may apply fluid pressure toa differential area of the second land of the fourth shift valve to keepthe fourth shift valve in the second position during an electricalfailure occurring in a high forward range. The high forward range may bea forward range higher than a third forward range.

According to another aspect, an electro-hydraulic control for amulti-speed vehicle transmission is provided, including an electricalcontrol configured to receive shift request signals from an electronicrange selector of the transmission, at least one trim system actuatableby the electrical control to control the rate of delivery of pressurizedhydraulic fluid to at least one shift mechanism of the transmission, aplurality of electro-hydraulic actuators each configured to receiveelectrical signals from the electrical control, a plurality of shiftvalves each being in fluid communication with an electro-hydraulicactuator to receive pressurized hydraulic fluid output by theelectro-hydraulic actuator and being in fluid communication with atleast one trim system and each other to selectively deliver pressurizedhydraulic fluid to at least one shift mechanism of the transmission, ashift by wire shift valve configured to selectively deliver pressurizedhydraulic fluid to at least one shift mechanism of the transmission, anda plurality of fluid passages selectively coupling the first, second,third, and fourth shift valves, the at least one trim system, and theshift by wire valve to provide a neutral range in which the neutralrange is maintained unless a change in position of at least one of theshift valves or shift by wire valve and actuation of at least one of thetrim systems occurs.

The shift by wire valve may have a first position in which it is notelectrically actuated and a second position in which it is electricallyactuated. The neutral range may be achievable whether the shift by wirevalve is in the first position or the second position. The at least onetrim system may be in direct fluid communication with at least one ofthe shift valves other than the shift by wire valve.

Patentable subject matter may include one or more features orcombinations of features shown or described anywhere in this disclosureincluding the written description, drawings, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description refers to the following figures in which:

FIG. 1 is a simplified block diagram of a motor vehicle powertrainincluding an electro-hydraulic control system having an electronicallycontrolled range valve in accordance with the present invention;

FIG. 2 is a schematic diagram of one embodiment of a control system fora multi-speed transmission for a motor vehicle, showing a fluid passagearrangement and fluid pressure configuration for a reverse range of thetransmission;

FIG. 3 is a schematic diagram of the embodiment of FIG. 2, showing afluid passage arrangement and fluid pressure configuration for anotherreverse range;

FIG. 4 is a schematic diagram of the embodiment of FIG. 2, showing afluid passage arrangement and fluid pressure configuration for a neutralrange;

FIG. 5 is a schematic diagram of the embodiment of FIG. 2, showing afluid passage arrangement and fluid pressure configuration for a firstforward range of the transmission;

FIG. 6 is a schematic diagram of the embodiment of FIG. 2, showing afluid passage arrangement and fluid pressure configuration for a secondforward range of the transmission;

FIG. 7 is a schematic diagram of the embodiment of FIG. 2, showing afluid passage arrangement and fluid pressure configuration for a fourthforward range of the transmission;

FIG. 8 is a schematic diagram of the embodiment of FIG. 2, showing afluid passage arrangement and fluid pressure configuration for thereverse range of FIG. 2, in a failure mode in response to an electricalfailure;

FIG. 9 is a schematic diagram of the embodiment of FIG. 2, showing afluid passage arrangement and fluid pressure configuration for thereverse range of FIG. 3, in a failure mode in response to an electricalfailure;

FIG. 10 is a schematic diagram of the embodiment of FIG. 2, showing afluid passage arrangement and fluid pressure configuration for theneutral range of FIG. 4, in a failure mode in response to an electricalfailure;

FIG. 11 is a schematic diagram of the embodiment of FIG. 2, showing afluid passage arrangement and fluid pressure configuration for the firstforward range of FIG. 5, in a failure mode after an electrical failure;

FIG. 12 is a schematic diagram of the embodiment of FIG. 2, showing afluid passage arrangement and fluid pressure configuration of the secondforward range of FIG. 6, in a failure mode after an electrical failure;and

FIG. 13 is a schematic diagram of the embodiment of FIG. 2, showing afluid passage arrangement and fluid pressure configuration of the fourthforward range of FIG. 7, in a failure mode after an electrical failure.

In general, like structural elements on different figures refer toidentical or functionally similar structural elements, althoughreference numbers may be omitted from certain views of the drawings forease of illustration.

DETAILED DESCRIPTION

Aspects of the present invention are described with reference to certainillustrative embodiments shown in the accompanying drawings anddescribed herein. While the present invention is described withreference to the illustrative embodiments, it should be understood thatthe present invention as claimed is not limited to the disclosedembodiments.

FIG. 1 depicts a simplified block diagram of an electro-hydraulictransmission control 20 including a shift by wire valve 26, in thecontext of an exemplary vehicle powertrain 10. The lines shown asconnecting blocks 12, 14, 16, 18, 20, 22, 24, 26, 28 of powertrain 10represent connections which, in practice, may include one or moreelectrical, mechanical and/or fluid connections, passages, couplings orlinkages, as will be understood by those skilled in the art and asdescribed herein.

Powertrain 10 includes drive unit 12, torque converter 14, torqueconverter clutch 16, transmission 18, electro-hydraulic control 20,electronic control 22, range selector 24, and final drive 28. Drive unit12 generally provides a torque output to torque converter 14. Drive unit12 may be an internal combustion engine of a compression-ignition type(i.e. diesel) or a spark-ignition type (i.e. gasoline), a hybrid unit,or other suitable unit for generating torque output to drive a vehicle.

Torque converter 14 selectively establishes a coupling between driveunit 12 and transmission 18 to convert and/or transfer the torque outputfrom drive unit 12 to the vehicle transmission 18. Such coupling is afluid coupling when torque converter clutch 16 is not applied, and amechanical coupling when torque converter clutch is applied. Torqueconverter clutches are often provided to effect unitary rotation of thetorque converter pump and turbine in response to reduced hydraulicpressure within the torque converter, which may occur when “slip” (i.e.,a difference in rotational speed) between the torque converter pump andturbine is not required.

Transmission 18 includes an input shaft, an output shaft, an assembly ofgears, and a plurality of gear-shifting mechanisms that are selectivelyengaged and disengaged by electro-hydraulic transmission control 20 tocause the vehicle to assume one of a plurality of operational modes orranges including at least six forward speed ratios, a neutral range, andat least one reverse range. As such, the shift mechanisms oftransmission 18 are in fluid communication with hydraulic controlelements of control 20.

In this disclosure, the term “shift mechanism” may be used to refer toone or more clutches, brakes, or other friction elements or devices, orsimilar suitable mechanisms configured to cause the transmission toswitch from one range or gear ratio to another, different range or gearratio.

Control 20 includes a two-position shift valve 26 that allows forshifting into reverse and neutral ranges when in one position and allowsfor shifting into forward ranges when in its other position. In theillustrated embodiment, reverse and neutral ranges are achieved whenshift valve 26 is in an off or de-actuated position and forward rangesare achievable when shift valve 26 is in the on or actuated position.Thus, shift valve 26 can control three modes of operation (reverse,neutral, and forward ranges) with only two positions. The structure andoperation of shift valve 26 is described in more detail below.

The embodiment of control 20 including shift valve 26 shown in FIGS.2-13 relates to a six-speed vehicle transmission that includes threeplanetary gearsets and five shift mechanisms (e.g. two rotating shiftmechanisms and three stationary shift mechanisms C1, C2, C3, C4, C5).During normal operation of transmission 18, two shift mechanisms areengaged in each range except neutral. An illustrative embodiment oftransmission 18 is disclosed in U.S. Pat. No. 4,070,927 to Polak, whichis incorporated herein by this reference. Those of ordinary skill in theart will understand that such transmission is offered only as anexample, and that aspects of the present invention are applicable toother multi-speed vehicle transmissions. In the illustrated embodiment,transmission 18 has a shift schedule as shown in Table 1 below.

TABLE 1 Clutches Range Applied Reverse C3, C5 Neutral C5 1st C1, C52^(nd) C1, C4 3^(rd) C1, C3 4^(th) C1, C2 5^(th) C2, C3 6^(th) C2, C4

While the illustrated embodiment specifies a particular shift schedule,it will be understood that in other embodiments, other combinations ofshift mechanisms C1, C2, C3, C4, and C5 may be applied and released toachieve particular operating ranges of the transmission.

The torque output by transmission 18 is applied to the final drive 28.The final drive 20 generally includes the drive wheels and driven loadmass carried by the vehicle. Characteristics of final drive 20 may varyconsiderably over the course of the vehicle's use, as may be the caseparticularly with commercial vehicles such as trucks, buses, emergencyvehicles, and the like.

Electrical control 22 controls operation of transmission 18 based oninputs from one or more components of drive unit 12, torque converter14, transmission 18, range selector 24; and/or other inputs. Such inputsmay include electrical digital and/or analog signals received fromsensors, controls or other like devices associated with the vehiclecomponents. For instance, inputs may include signals indicative oftransmission input speed, driver requested torque, engine output torque,engine speed, temperature of the hydraulic fluid, transmission outputspeed, turbine speed, brake position, gear ratio, torque converter slip,and/or other measurable parameters.

Electrical control 22 generally includes electrical circuitry configuredto process, analyze or evaluate one or more of the inputs and issueelectrical control signals to appropriate components ofelectro-hydraulic control system 20, as needed, through one or moreelectrical lines, conductors, or other suitable connections. Suchconnections may include hard-wired and/or networked components in anysuitable configuration including, for example, insulated wiring and/orwireless transmission as may be appropriate or desired.

Range selector 24 issues signals or commands indicative of a selected ordesired operational mode of the vehicle, i.e., a selected or desiredforward speed ratio, a desired reverse range, or neutral. In theillustrated embodiment, range selector 24 is anelectronically-controlled or “shift-by-wire” range selecting mechanism,rather than a manual selector.

As shown in FIGS. 2-16, control 20 includes two-position shift valve 26,three additional shift valves 36, 38, 40, and three clutch pressurecontrol or “trim” systems 30, 32, and 34.

Fluid circuits, including a main pressure circuit 60, a control pressurecircuit 62, and an exhaust circuit 64, are coupled to a source ofpressurized fluid (not shown). Fluid circuits 60, 62, 64 fluidly couplethe hydraulic components of control 20 to one another as shown anddescribed below.

During operation of a vehicle into which control 20 is incorporated,main pressure circuit 60 draws hydraulic fluid at a main pressure from afluid supply, such as a sump or reservoir (not shown). In general, themain pressure defines a range including a minimum system pressure and amaximum system pressure for main pressure circuit 60. In the illustratedembodiment, the main pressure is in the range of about 50-250 pounds persquare inch (psi). In the drawings, main pressure is denoted using abackward-slash pattern.

Control pressure circuit 62 circulates hydraulic fluid at a controlpressure, which is typically regulated by a regulator or modulator valveas will be understood. In the illustrated embodiment, the controlpressure is generally in the range of about 50-110 psi. Control pressureis denoted in the drawings by a dotted pattern.

Exhaust circuit 64 is in fluid communication with components of control20 as shown in the drawings. Exhaust pressure is in the range of aboutzero psi. Exhaust circuit 64 is operably coupled to an exhaust backfillregulator valve 44. The EBF valve 44 provides an exhaust backfillpressure, which is configured to prevent air from entering exhaustedclutches. In the illustrated embodiment, the exhaust backfill pressureis generally in the range of about 2 psi. In the drawings, exhaustpressure is denoted by a forward-slash pattern.

Also shown are restrictors or orifices 80, 82, 84, 86, 88. Therestrictors or orifices 80, 82, 84, 86, 88 are positioned in fluidpassages to alter or moderate the rate of fluid flow through thepassages or a portion thereof, in order to control the rate at whichpressure in a fluid passage changes. These elements are typically usedto provide additional control over fluid pressure in the passages. Forexample, series of orifices 80, 82, 84 are used to prevent actuation ofpressure switches 72, 74, 76 from occurring until their correspondingshift valve 38, 40, 26 is fully stroked.

Electro-hydraulic actuators 50, 52, 54, 56, and pressure switches 70,72, 74, 76 are in fluid communication with each of the shift valves 36,38, 40, 26, respectively. It will be understood that actuators 50, 52,54, 56, and pressure switches 70, 72, 74, 76 are electrically coupled tocontrol 22, although for ease understanding these electrical connectionsare not shown in FIGS. 2-16.

In general, each of the valves of control 20 includes a valve head, avalve spool, at least one valve land interposed between portions of thevalve spool or between the valve head and a portion of the valve spool,and a return spring disposed in a spring chamber. Each valve spool isaxially translatable in a valve bore in response to changes in fluidpressure or fluid flow through the various passages of control 20. Forease of illustration, the valve bores have been omitted from thefigures.

The valve lands each define a diameter that is greater than the diameterdefined by the valve spool, such that surfaces of the lands may slidablyengage interior surfaces of the valve bore when the valve spooltranslates within the valve bore. Spool portions between valve lands mayselectively connect fluid passages to other fluid passages, or connectfluid passages to fluid chambers, depending on the position of thevalve.

Each of shift valves 36, 38, 40 has more than four spaced-apart landsthat define at least four fluid chambers therebetween. Shift valve 26has four spaced-apart lands that define three fluid chamberstherebetween.

Shift valves 36 and 40 are generally single-diameter shift valves,meaning that all of the valve's lands have substantially the samediameter or there is no pressure differential. Shift valve 38 is atwo-diameter shift valve, with land 166 having a smaller diameter thanland 168, as best shown in FIGS. 8 and 10. The land above land 166(nearest the valve head) on shift valve 38 has substantially the samediameter as land 166, and the lands below land 168 (nearer to the returnspring) have substantially the same diameter as land 168.

Shift valve 26 is a three-diameter shift valve. Land 172 has a largerdiameter than land 170, and land 174 has a larger diameter than land 172as best shown in FIGS. 11-13. Land 176 has substantially the samediameter as land 174. The height of land 174 is smaller than the heightsof the other lands 170, 172 and 176.

The multiple diameters on shift valves 26, 38 allow control 20 to usevalve latching to provide failure recovery from any range oftransmission 18 in the event of an electrical failure. The latchingfeatures on shift valve 26 additionally serve to hold shift valve 26 inthe stroked position as long as a forward range is commanded, therebypreventing an unintended shift out of a forward range in the event thatshift valve 26 fails. These latching features of shift valves 26, 38 aredescribed in greater detail below.

As is well known, return springs 180, 182, 184, 186, 188 bias theirrespective valve in a destroked position. Changes in fluid pressure orfluid flow in selected fluid passages may cause the valve spool totranslate within the valve bore, causing the return spring to partiallyor fully compress.

Responsive to the output of actuators 50, 52, 54, 56, shift valves 36,38, 40, 26 are slidable between the destroked position and a strokedposition, where the stroked position is one in which the return springis fully compressed. In the illustrated embodiment, each of actuators50, 52, 54, 56 is a solenoid valve of the on/off type. The positioningof the shift valves 36, 38, 40, 26 determines which of the shiftmechanisms C1, C2, C3, C4, C5 receive fluid pressure and which do not,thereby controlling which shift mechanisms are applied and which arereleased at any given time.

The pressure control valves of clutch trim systems 30, 32, 34 areconfigured to assume intermediate positions between the first and secondpositions, in which the return spring is partially compressed, inaddition to the first and second positions. As will be understood, thedisplacement of the pressure control valves of the clutch trim systems30, 32, 34 is controlled by electro-hydraulic actuators that have avariable output pressure, such as variable-bleed solenoids. Because therate of application of fluid pressure can be controlled in this way,clutch trim systems 30, 32, 34 control the rate at which a shiftmechanism is applied or released. Clutch trim systems 30 and 32 controlthe rate of application or release of the shift mechanisms C1, C2, C3,C4, C5 (depending on the positioning of the shift valves 26, 36, 38,40), while clutch trim system 34 controls the rate of application orrelease of torque converter clutch 14.

Actuators 50, 52, 54, 56 and the variable-output electro-hydraulicactuators of the clutch trim systems 30, 32, 34 are operably coupled tocontrol 22 to receive electrical signals (i.e. electrical current)therefrom. The electrical signals generated and sent by control 22 tothe electro-hydraulic actuators of control 20 selectively actuate thevalves (in response to driver input or other inputs) to accomplishshifting of transmission 18.

Each of the electro-hydraulic actuators of control 20 is either of thenormally low type or of the normally high type. A normally low (ornormally off) solenoid valve provides maximum output pressure when itreceives electrical input and provides zero or minimum output pressurewhen no electrical input is received; while a normally high (or normallyon) solenoid valve provides maximum output pressure when it is notreceiving any electrical input and provides zero or minimum outputpressure when electrical input is provided. Thus, as used herein, whenreferring to an actuator or solenoid valve as being “actuated,” thismeans either that electrical input is supplied to the solenoid (as inthe case of normally low solenoids) or that electrical input is notsupplied to the solenoid (as in the case of normally high solenoids).

In the illustrated embodiment, each of actuators 50, 52, 54, 56 is anormally low solenoid, the electro-hydraulic actuators of trim systems32 and 34 are normally low solenoids, and the electro-hydraulic actuatorof trim system 30 is a normally high solenoid.

In general, pressure switches 70, 72, 74, 76 are each configured toissue an electrical output signal to control 22 in response to apredetermined fluid pressure being detected by the pressure switch, fordiagnostic purposes or for other reasons. Such electrical signals informcontrol 22 of changes in status of components of control 20. Generationof an output signal by pressure switches 70, 72, 74 can be triggeredeither by the presence or the absence of a predetermined level of fluidpressure, depending on the configuration of the switch. As used herein,the term “actuated” when used to describe activity of a pressure switchmeans simply that the switch has issued an output signal to control 22,without limiting the pressure switch to a particular type orconfiguration.

In the illustrated embodiment, each shift valve 26, 36, 38, 40 has acorresponding pressure switch 76, 70, 72, 74, in fluid communicationtherewith. Each of pressure switches 70, 72, 74, 76 acts as a binaryswitch such that it is actuated when the shift valve to which it iscoupled is in the stroked position. Control 20 may include otherpressure switches in addition to those used to monitor the position ofthe shift valves. For example, control 20 may use pressure switches todetect changes in position of the trim valves 30, 32, 34.

Table 2 shows a steady state mechanization of components of control 20during normal operation. The number “1” is used to denote that acomponent is actuated, while the number “0” denotes that a component isnot actuated. The mechanization of trim system 34 is omitted from Table2 because the application of torque converter clutch 34 is controlledindependently by trim system actuator 58.

TABLE 2 Trim Shift Shift Shift Trim System System Valve Valve ValveShift Valve Range 30 32 36 38 40 26 Reverse1 1 1 0 1 1 0 Reverse2 1 1 10 1 0 Neutral 1 0 1 1 1 0 1st 1 0 0 1 0 1 2^(nd) 0 1 0 0 0 1 3^(rd) 1 01 0 0 1 4^(th) 0 1 1 0 1 1 5^(th) 1 0 0 0 1 1 6^(th) 0 1 0 0 1 1

The configuration of control 20 during normal operation, including twopossible reverse ranges, a neutral range, and multiple forward ranges,will now be described.

As shown in Table 2 and FIGS. 2-3, control 20 provides two alternativereverse ranges. In the reverse range of FIG. 2, denoted as “Reverse1” inTable 2, shift valve actuators 52 and 54 are actuated, causing shiftvalves 38 and 40 to move to the stroked position while shift valve 36remains in the destroked position due to actuator 50 being non-actuated.Trim system 30 is fluidly coupled to fluid chamber 148 as a result ofactuation of shift valve 38 by actuator 52. As a result, trim system 30applies main pressure to shift mechanism C5 through fluid chamber 148and fluid passage 94.

In the Reverse1 range, trim system 32 is fluidly coupled to fluidchamber 150 via fluid chamber 144 of shift valve 36, fluid passage 100,fluid chamber 152 of shift valve 40, and fluid passage 98. As a result,trim system 32 applies main pressure to shift mechanism C3 via fluidchamber 150 and fluid passage 96.

Shift valve 26 is not actuated in the Reverse1 range. However, even ifshift valve 26 were actuated in the Reverse1 range, control 20 wouldremain in the Reverse1 range because the fluid passages 104, 108 (whichfeed shift mechanisms C1, C2 respectively when shift valve 26 isstroked) are connected to exhaust pressure. Thus, the Reverse1 range canbe achieved and maintained regardless of the position of shift valve 26.Moreover, in order for control 20 to fail to a forward range, two valvemalfunctions would have to occur, e.g. a failure of shift valve 26 and afailure of at least one of the other shift valves 36, 38, 40, or afailure of shift valve 26 and a failure of one of the trim systems 30,32.

In the reverse range of FIG. 3, denoted as “Reverse2” in Table 2, theshift mechanisms fed by trim systems 30, 32 are reversed relative to theReverse1 range. In Reverse2, trim system 30 supplies main pressure toshift mechanism C3 via fluid chamber 150 of shift valve 38, and trimsystem 32 supplies main pressure to shift mechanism C5 via fluid chamber138 of shift valve 36, fluid passage 114, fluid chamber 156 of shiftvalve 40, fluid passage 104, fluid chamber 194 of shift valve 26, fluidpassage 134, fluid chamber 164 of trim valve 34, fluid passage 118,orifices 87, 88, fluid chamber 148 of shift valve 38 and fluid passage94. Shift mechanisms C3 and C5 are applied in both the Reverse1 andReverse2 ranges.

A neutral range configuration of control 20 is shown in FIG. 4. In theneutral range, all three shift valves 36, 38, 40 are actuated by controlpressure supplied by actuators 50, 52, 54 respectively. As a result,pressure switches 70, 72, 74 are actuated. Shift valve 26 is notactuated in the neutral range and therefore, the neutral range can beattained and maintained independently of shift valve 26.

In the neutral range, trim system 30 supplies main pressure to shiftmechanism C5 via passage 128, fluid chamber 148, and passage 94. Inorder to transition from the neutral range of FIG. 4 to either of thereverse ranges of FIGS. 2 and 3, trim system 32 would have to beactuated and either shift valve 36 (for Reverse1 range) or shift valve38 (for Reverse2 range) would have to change position. Similarly, inorder to transition from the neutral range of FIG. 4 to a forward range,shift valve 26 and at least one other shift valve 36, 38, 40 have tochange position. Thus, control 20 provides protection againstunintentional shifting out of neutral into a moving range by requiringat least two valves to change position.

Exemplary forward range configurations of control 20 are shown in FIGS.5, 6, and 7. Each of the forward ranges requires either shift mechanismC1 or shift mechanism C2 to be applied. Both shift mechanism C1 and C2are in fluid communication with shift valve 26. When shift valve 26 isnot actuated (i.e. destroked), both shift mechanism C1 and shiftmechanism C2 are in direct fluid communication with exhaust backfillcircuit 64 and EBF valve 44 as shown in FIGS. 2-4. Movement of shiftvalve 26 to the on or stroked position is initiated by actuator 56independently of the other valve systems of control 20. Thus, shiftingfrom a non-forward range into a forward range can only be accomplishedif shift valve 26 is in the actuated or stroked position shown in FIGS.5, 6, and 7. Thus, shift valve 26 is in the on or stroked position inall forward ranges, as indicated by Table 2.

Movement of shift valve 26 to the stroked position requires actuation ofactuator 56. Actuator 56 is actuated by electrical signals issued bycontrol 22 in response to a forward range request received from rangeselector 24 in the form of an electrical signal. In this way, control 20is configured so that transitions from non-forward ranges to a forwardrange only occur if an electrical forward range request signal has beenreceived by control 22.

FIG. 5 shows a configuration of control 20 for a first forward range inwhich trim system 30 applies main pressure to shift mechanism C5 viafluid chamber 148 of shift valve 38. Actuation of shift valve 26 byactuator 56 places shift mechanism C1 in fluid communication with mainpressure via fluid chamber 192 of shift valve 26, fluid passage 104 andfluid chamber 156 of shift valve 40.

FIG. 6 shows a configuration of control 20 for a second forward range inwhich trim system 30 applies main pressure to shift mechanism C4 viafluid chamber 144 of shift valve 36, passage 100, and fluid chamber 154of shift valve 40. Main pressure is applied to shift mechanism C1 asdescribed above with regard to FIG. 5.

FIG. 7 illustrates a configuration of control 20 for a fourth forwardrange in which main pressure is applied to shift mechanisms C1 and C2.Main pressure is applied to shift mechanism C1 as described above withregard to FIG. 5. Main pressure is applied to shift mechanism C2 viafluid chamber 190 of shift valve 26, fluid passage 108, fluid chamber136 of shift valve 38, fluid passage 196, and fluid chamber 158 of shiftvalve 40. FIG. 7 also illustrates the application of torque converterclutch 14 by actuator 58, which by applying control pressure to the headof trim valve 34, connects main pressure from passage 116 with thetorque converter clutch 14. Since main pressure flows through passage116 in all of the normal modes of operation of control 20, torqueconverter clutch 14 can by actuated by actuator 58 at any time (i.e., inany range).

Table 3 shows a steady state mechanization of components of control 20in a failure mode resulting from an electrical failure. The number “1”is used to denote that a component is actuated, while the number “0”denotes that a component is not actuated. The letter “H” is used toindicate that a component is hydraulically held in position in theabsence of electrical input. The mechanization of trim system 34 isomitted since the torque converter clutch 34 is not applied during anelectrical failure.

TABLE 3 Trim Shift Shift Shift Shift Trim System System Valve ValveValve Valve Range Fails To 30 32 36 38 40 26 Reverse1 Neutral 1 0 0 H H0 (C5) Reverse2 Neutral 1 0 0 0 H 0 (C3) Neutral Neutral 1 0 0 H H 0(C5) 1st 1^(st) 1 0 0 H 0 H 2^(nd) 3^(rd) 1 0 0 0 0 H 3^(rd) 3^(rd) 1 00 0 0 H 4^(th) 5^(th) 1 0 0 0 H H 5^(th) 5^(th) 1 0 0 0 H H 6^(th)5^(th) 1 0 0 0 H H

FIGS. 8-13 show the configuration of control 20 in the event of anelectrical failure in the Reverse1, Reverse2, neutral, and first, secondand fourth forward ranges in accordance with Table 3. Trim system 30 isactuated by a normally high solenoid and is therefore actuated in theevent of an electrical failure. Thus, trim system 30 applies mainpressure to either shift mechanism C5 or shift mechanism C3, dependingon the position of shift valve 38, in the event of an electricalfailure.

When shift valve 38 is stroked during normal operation, trim system 30is fluidly coupled to shift mechanism C5. This is the case in theReverse1, neutral, and first forward ranges as shown in FIGS. 2, 4 and5. If an electrical failure occurs in one of these ranges, actuator 52will not deliver pressure to shift valve 38 because of the absence ofelectrical input. However, the stroked position of shift valve 38 ismaintained because trim system 30 applies main pressure to thedifferential area d3 of land 168 of shift valve 38 via fluid chamber148. This is shown in FIGS. 8 (Reverse1), 10 (neutral), and 11 (1^(st)forward range).

Since normally high trim system 30 controls both shift mechanisms C5 andC3, and the reverse ranges require both C3 and C5 to be applied, in theevent of an electrical failure, the reverse ranges cannot fail toreverse. Instead, both of the reverse ranges will fail to a neutralrange as shown in FIGS. 8 and 9 and indicated in Table 3 above.

The Reverse1 range fails to a neutral state in which the C5 shiftmechanism is applied as shown in FIG. 8. The Reverse2 range fails to aneutral state in which the C3 shift mechanism is applied as shown inFIG. 9. The neutral range fails to the failure mode C5 neutral stateshown in FIG. 10. The failure mode C5 and C3 neutral states cannot beshifted out of as long as the electrical failure occurs, becauseshifting out of neutral to either a reverse range or forward rangerequires electrical input.

FIGS. 8, 9, and 10 also show how the flow of control pressure to thehead of shift valve 40, via fluid chamber 140 of shift valve 36 andfluid passage 108, maintains the stroked position of shift valve 40 inthe absence of electrical input to actuator 54. When shift valve 40 isstroked, main pressure is blocked from entering passage 104, which is influid communication with shift valve 26.

FIGS. 11, 12, and 13 show failure mode configurations of control 20 forforward ranges. As shown in FIG. 11, the first forward range ismaintained in the event of an electrical failure due to the latching ofshift valve 38 by pressure applied to the differential area of land 168,and the latching of shift valve 26. Pressure applied to the differentialarea of land 174 maintains the stroked position of shift valve 26 in theabsence of electrical input to actuator 56.

The second and third forward ranges fail to the third forward range inthe event of an electrical failure, as shown in FIG. 12. The shift valve26 is latched as described above with reference to FIG. 11. Duringnormal operation, shift valve 38 is destroked in the second and thirdforward ranges. The destroked position is maintained in the event ofelectrical failure because the lands below land 168 have the samediameter as land 168. However, shift mechanism C3 is applied (if thefailure occurred in the second forward range) or maintained (if thefailure occurred in the third forward range) because the actuator fortrim system 30 is of the normally high type.

The fourth and higher forward ranges fail to the fifth forward range inthe event of an electrical failure as shown in FIG. 13. In theelectrical failure mode for these ranges, shift valve 26 is latched inthe stroked position by pressure applied to the differential area ofland 172. Thus, main pressure is supplied to shift mechanism C2 asdescribed above with regard to FIG. 7. Shift valve 40 is hydraulicallylatched by control pressure via passage 102 as described above. Trimsystem 30 applies main pressure to shift mechanism C3 because shiftvalve 38 is destroked.

In all forward ranges, the latching features on shift valve 26 incommunication with shift mechanisms C1 and C2 as described above holdshift valve 26 in the stroked position as long as the transmission isreceiving a forward range command from electrical control 22 or rangeselector 24, thereby providing protection against a mechanical failureof shift valve 26 that might otherwise cause shift valve 26 toerroneously move to the destroked position.

The hydraulic latching of shift valves 26, 38 and 40 in the variousinstances described above is maintained unless the pressure of thehydraulic fluid in the control system decreases to a point where it canno longer overcome the bias of the valve's return spring, such as is thecase when the source of pressurized hydraulic fluid (e.g., the enginepump) is turned off.

The present disclosure describes patentable subject matter withreference to certain illustrative embodiments. The drawings are providedto facilitate understanding of the disclosure, and may depict a limitednumber of elements for ease of explanation. Except as may be otherwisenoted in this disclosure, no limits on the scope of patentable subjectmatter are intended to be implied by the drawings. Variations,alternatives, and modifications to the illustrated embodiments may beincluded in the scope of protection available for the patentable subjectmatter.

1. An electro-hydraulic control for a multi-speed vehicle transmission,comprising: an electrical control configured to receive shift requestsignals from an electronic range selector of the transmission, first,second, and third electro-hydraulic actuators each configured to receiveelectrical signals from the electrical control, first, second and thirdshift valves each being in fluid communication with the first, second,and third electro-hydraulic actuators to receive pressurized hydraulicfluid output by the electro-hydraulic actuators and being in fluidcommunication with each other to selectively deliver pressurizedhydraulic fluid to at least one shift mechanism of the transmission, afourth electro-hydraulic actuator configured to receive electricalsignals from the electrical control, a fourth shift valve configured toselectively deliver pressurized hydraulic fluid to at least one shiftmechanism of the transmission, the fourth shift valve being controllableby the fourth electro-hydraulic actuator to achieve a first positionwhen the fourth electro-hydraulic actuator is not electrically actuatedand a second position when the fourth electro-hydraulic actuator iselectrically actuated, and a plurality of fluid passages selectivelycoupling the first, second, third, and fourth shift valves such that aneutral or reverse range can be achieved by the transmission when thefourth shift valve is in either the first position or the secondposition and a forward range can be achieved by the transmission onlywhen the fourth shift valve is in the second position.
 2. Theelectro-hydraulic control of claim 1, wherein the plurality of fluidpassages selectively couple the first, second, third, and fourth shiftvalves such that a first reverse range can be achieved whether thefourth shift valve is in the first position or the second position. 3.The electro-hydraulic control of claim 1, wherein the plurality of fluidpassages selectively couple the first, second, third, and fourth shiftvalves such that the neutral range can be achieved whether the fourthshift valve is in the first position or the second position.
 4. Theelectro-hydraulic control of claim 1, wherein the fourth shift valve hasa first fluid chamber fluidly coupled to a first shift mechanism and asecond fluid chamber fluidly coupled to a second shift mechanism, thefirst shift valve has a third fluid chamber fluidly coupled to a thirdshift mechanism, the third shift valve has a fourth fluid chamberfluidly coupled to a fourth shift mechanism, and the first shift valvehas a fifth fluid chamber fluidly coupled to a fifth shift mechanism ofthe transmission.
 5. The electro-hydraulic control of claim 4, whereinthe second shift valve is fluidly coupled to the third shift mechanismthrough the first and third shift valves in a first reverse range andthe second shift valve is fluidly coupled to the fifth shift mechanismthrough the first, third, and fourth shift valves in a second reverserange.
 6. The electro-hydraulic control of claim 5, comprising a torqueconverter clutch control valve, wherein the torque converter clutchcontrol valve is coupled to at least one of the first, second, third andfourth shift valves.
 7. The electro-hydraulic control of claim 1,wherein the plurality of fluid passages selectively couple the first,second, third and fourth shift valves such that at least two of theshift valves are required to change position in order for thetransmission to shift from a neutral range to a forward range.
 8. Theelectro-hydraulic control of claim 7, comprising first and second trimsystems each configured to receive electrical signals from theelectrical control and control the rate at which fluid pressure isdelivered to the shift mechanisms of the transmission via the first,second, third, and fourth shift valves, wherein the first trim system isdirectly fluidly coupled to the first shift valve, the second trimsystem is directly fluidly coupled to the second shift valve, the secondtrim system is fluidly coupled to the third shift valve via the secondshift valve, and the second trim system is fluidly coupled to the firstshift valve via the second and third shift valves.
 9. Theelectro-hydraulic control of claim 8, wherein the plurality of fluidpassages selectively couple the first, second, third and fourth shiftvalves such that at least one of the trim systems and at least one ofthe shift valves are required to be actuated in order for thetransmission to shift from a neutral range to a reverse range.
 10. Anelectro-hydraulic control for a multi-speed vehicle transmission,comprising: an electrical control configured to receive shift requestsignals from an electronic range selector of the transmission, at leastone trim system actuatable by the electrical control to control the rateof delivery of pressurized hydraulic fluid to at least one shiftmechanism of the transmission, first, second, and thirdelectro-hydraulic actuators each configured to receive electricalsignals from the electrical control, first, second and third shiftvalves each being in fluid communication with the first, second, andthird electro-hydraulic actuators to receive pressurized hydraulic fluidoutput by the electro-hydraulic actuators and being in fluidcommunication with at least one trim system and each other toselectively deliver pressurized hydraulic fluid to at least one shiftmechanism of the transmission, a fourth electro-hydraulic actuatorconfigured to receive electrical signals from the electrical control,and a fourth shift valve configured to selectively deliver pressurizedhydraulic fluid to first and second shift mechanisms of thetransmission, the fourth shift valve being controllable by the fourthelectro-hydraulic actuator to achieve a first position when the fourthelectro-hydraulic actuator is not electrically actuated and a secondposition when the fourth electro-hydraulic actuator is electricallyactuated, the fourth shift valve being configured to maintain the firstposition if the fourth shift valve is in the first position when anelectrical failure occurs, and the fourth shift valve being configuredto maintain the second position if the fourth shift valve is in thesecond position and a first trim system is actuated when an electricalfailure occurs, wherein the first trim system selectively applies fluidpressure to the first and second shift mechanisms depending on theposition of the fourth shift valve, in the event of an electricalfailure.
 11. The electro-hydraulic control of claim 10, wherein thefourth shift valve has at least first, second and third spaced-apartlands, the first and second lands define a second fluid chamber that isin fluid communication with the second shift mechanism and the secondand third lands define a first fluid chamber that is in fluidcommunication with the first shift mechanism.
 12. The electro-hydrauliccontrol of claim 11, wherein fluid in the first and second fluidchambers of the fourth shift valve is at an exhaust pressure in neutraland reverse ranges during normal operation and the fluid in the firstand second fluid chambers of the fourth shift valve is at an exhaustpressure in neutral and reverse ranges during an electrical failure. 13.The electro-hydraulic control of claim 11, wherein the first land has afirst diameter, the second land has a second diameter, the third landhas a third diameter, the second diameter is larger than the firstdiameter, and the third diameter is larger than the second diameter. 14.The electro-hydraulic control of claim 11, wherein fluid pressure isapplied to a differential area of the third land of the fourth shiftvalve to keep the fourth shift valve in the second position during anelectrical failure occurring in a low forward range.
 15. Theelectro-hydraulic control of claim 14, wherein the low forward range isa forward range lower than a fourth forward range.
 16. Theelectro-hydraulic control of claim 11, wherein fluid pressure is appliedto a differential area of the second land of the fourth shift valve tokeep the fourth shift valve in the second position during an electricalfailure occurring in a high forward range.
 17. The electro-hydrauliccontrol of claim 16, wherein the high forward range is a forward rangehigher than a third forward range.
 18. An electro-hydraulic control fora multi-speed vehicle transmission, comprising: an electrical controlconfigured to receive shift request signals from an electronic rangeselector of the transmission, at least one trim system actuatable by theelectrical control to control the rate of delivery of pressurizedhydraulic fluid to at least one shift mechanism of the transmission, aplurality of electro-hydraulic actuators each configured to receiveelectrical signals from the electrical control, a plurality of shiftvalves each being in fluid communication with one of the plurality ofelectro-hydraulic actuators to receive pressurized hydraulic fluidoutput by the electro-hydraulic actuator and being in fluidcommunication with the at least one trim system and each other toselectively deliver pressurized hydraulic fluid to the at least oneshift mechanism of the transmission, the plurality of shift valvesincluding a first shift valve, a second shift valve, a third shiftvalve, and a fourth shift valve, a shift by wire shift valve configuredto selectively deliver pressurized hydraulic fluid to at least one shiftmechanism of the transmission, and a plurality of fluid passagesselectively coupling the first, second, third, and fourth shift valves,the at least one trim system, and the shift by wire valve to provide aneutral range in which the neutral range is maintained unless a changein position of at least one of the shift valves or shift by wire valveand actuation of at least one of the trim systems occurs; wherein theplurality of fluid passages selectively couple the first, second, third,and fourth shift valves such that at least one of the trim systems andat least one of the shift valves are required to be actuated in orderfor the transmission to shift from a neutral range to a reverse range.19. The electro-hydraulic control of claim 18, wherein the shift by wirevalve has a first position in which it is not electrically actuated anda second position in which it is electrically actuated, and the neutralrange is achievable whether the shift by wire valve is in the firstposition or the second position.
 20. The electro-hydraulic control ofclaim 19, wherein the at least one trim system is in direct fluidcommunication with at least one of the shift valves other than the shiftby wire valve.
 21. An electro-hydraulic control for a multi-speedvehicle transmission, comprising: an electrical control configured toreceive shift request signals from an electronic range selector of thetransmission, first, second, and third electro-hydraulic actuators eachconfigured to receive electrical signals from the electrical control,first, second and third shift valves each being in fluid communicationwith the first, second, and third electro-hydraulic actuators to receivepressurized hydraulic fluid output by the electro-hydraulic actuatorsand being in fluid communication with each other to selectively deliverpressurized hydraulic fluid to at least one shift mechanism of thetransmission, a fourth electro-hydraulic actuator configured to receiveelectrical signals from the electrical control, a fourth shift valveconfigured to selectively deliver pressurized hydraulic fluid to atleast one shift mechanism of the transmission, the fourth shift valvebeing controllable by the fourth electro-hydraulic actuator to achieve afirst position when the fourth electro-hydraulic actuator is notelectrically actuated and a second position when the fourthelectro-hydraulic actuator is electrically actuated, a plurality offluid passages selectively coupling the first, second, third, and fourthshift valves such that a neutral or reverse range can be achieved by thetransmission when the fourth shift valve is in either the first positionor the second position and a forward range can be achieved by thetransmission only when the fourth shift valve is in the second position,and first and second trim systems each configured to receive electricalsignals from the electrical control and control the rate at which fluidpressure is delivered to at least one shift mechanism of thetransmission via the first, second, third, and fourth shift valves, thefirst trim system being directly fluidly coupled to the first shiftvalve, the second trim system being directly fluidly coupled to thesecond shift valve, fluidly coupled to the third shift valve via thesecond shift valve, and fluidly coupled to the first shift valve via thesecond and third shift valves, wherein the plurality of fluid passagesselectively couple the first, second, third, and fourth shift valvessuch that at least two of the shift valves are required to changeposition in order for the transmission to shift from a neutral range toa forward range and at least one of the trim systems and at least one ofthe shift valves are required to be actuated in order for thetransmission to shift from a neutral range to a reverse range.